1. Field of the Invention
Embodiments of the present invention generally relate to cyclonic separation units. More particularly, embodiments of the present invention relate to high-pressure cyclones.
2. Description of the Related Art
Cyclonic separation involves separating a mixture of two or more phases, for example, fluid-particulate suspensions wherein one or more solid particulates are suspended in a carrier fluid, under a centrifugal force generated by centripetal motion. A cyclone separator is the mechanical device typically used to carry out cyclonic separation processes. In normal cyclone separator operation, a particulate suspension is introduced into the top of the cyclone separator via a tangential inlet where the solid particles tend to collect on the inner surface of the separator and its fluidic counterpart is entrained into a vortex. The solid particles gradually fall to the bottom of the separator vessel for further processing, while the fluidic counterpart is eventually drawn through a centrally-located output tube. Uses of cyclonic separation methods can include unit operations to purify a phase, to concentrate a phase, to terminate chemical and physical interactions between mixed phases, or combinations thereof.
In applications exhibiting high and ultrahigh pressures, cyclonic separation operations are typically undertaken by a pressure cyclone separator. Pressure cyclones generally consist of a compression-proof vessel that is geometrically and structurally designed to resist elevated pressures and temperatures. However, it is nonetheless not unheard of to employ pressure cyclones in low-pressure environments. In practice, a pressure cyclone can be manufactured to almost any size or dimension to fit any particular separation application.
At least one high-pressure application that is appropriate for a pressure cyclone includes hydrocarbon gasification processes, where carbonaceous materials, such as coal, petroleum, crude oil, tars, biofuel, or biomass, are converted into a “syngas,” such as carbon monoxide and hydrogen. Depending on the hydrocarbon used and the conversion process employed, pressures in a hydrocarbon gasification process can range from about 50 psi to about 1,000 psi, and even up to ultrahigh pressures of about 7,000 psi. Because of these potentially-extreme conditions, the structural design of pressure cyclones is a vital concern if it is to endure a long production life.
The top head and tangential inlet of the pressure cyclone are key components in improving the overall efficiency of high-pressure cyclonic separation processes. In prior applications, the top head has been designed as a flat surface near the inlet entrance, thereby creating joints and edges reflecting a significant propensity to fail under elevated pressures and temperatures. Prior applications have implemented a semi-spherical, convex top head to take advantage of the structural integrity of an arced surface in order to withstand the elevated pressures. However, the convex top head design essentially creates a void area between the tangential inlet and the top head where the vortex can be significantly disturbed, thereby resulting in a significant reduction in efficiency of the separation process.
Likewise, the casing surrounding the tangential inlet has often been designed with square or rectangular features that also have a tendency to fail or crack under extreme conditions. In applications using a continuously-circular inlet casing, the inlet nozzle is oftentimes required to be shifted into direct or semi-direct alignment with a centrally-located vortex output tube, thereby injecting particulate matter directly at the output tube which prematurely erodes its surface and disturbs the vortex. To remedy this, some designs have implemented a bend in the output tube, thereby placing it off-center from the vortex and effectively reducing the efficiency of the process.
What is needed, therefore, is an improved top head design and tangential inlet for pressure cyclones that can withstand elevated pressures and maintain or increase process efficiency.